An EL element has a problem that a luminance property such as luminance or evenness of luminance significantly deteriorates as compared with the beginning when it is driven for a certain period. This low reliability is a factor in the limited practical application.
As one factor of worsening reliability, water, oxygen or the like which enters into the EL element from outside is given.
Development of a display device that has a structure for preventing the deterioration of the EL element has been conducted. In addition, there is also a method by which a sealing material is formed over an insulator provided with an EL element, and an enclosed space surrounded by a covering material and the sealing material is filled with a filler composed of a resin or the like with the use of the sealing material so that the EL element is blocked off from outside (for example, refer to Patent Document 1)